VHF Imaging Radar Observations and Theory of Banded Midlatitude Sporadic E Ionization Layers
VHF Imaging Radar Observations and Theory of Banded Midlatitude Sporadic E Ionization Layers
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DOI：
10.1029/2021ja029257
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发表时间：
2021-04
期刊：
影响因子：
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通讯作者：
D. Hysell;M. Larsen
中科院分区：
文献类型：
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作者：
D. Hysell;M. Larsen
本文介绍并分析了在纽约伊萨卡用30 MHz相干散射雷达成像仪观测到的零星E（Es）层中场向等离子体密度不规则性的后向散射。雷达探测的体积位于地磁纬度约54°，在中纬度槽下，在Es层盛行的地带的最北方边缘。尽管如此，这些不规则性仍然表现出在中低纬度地区常见的准周期回波的许多特征。这些趋势包括在北方半球从西北向东南延伸的细长带中发生，并向西南传播，其中相隔数十公里。此外，发现不规则性表现出更精细的结构，次级带几乎垂直于初级带取向。我们研究了这样一个命题，即主带是由低热层中的中性开尔文-亥姆霍兹（KH）不稳定性引起的Es层结构的指示，而次级带则意味着次级KH不稳定性。KH的三维数值模拟结果支持这一命题。
Observations of backscatter from field‐aligned plasma density irregularities in sporadic E (Es) layers made with a 30‐MHz coherent scatter radar imager in Ithaca, New York are presented and analyzed. The volume probed by the radar lies at approximately 54° geomagnetic latitude, under the midlatitude trough and at the extreme northern edge of the zone where Es layers are prevalent. Nonetheless, the irregularities exhibit many of the characteristics of quasiperiodic echoes observed commonly at lower middle latitudes. These include a tendency to occur in elongated bands stretching from the northwest to southeast in the Northern hemisphere separated by tens of kilometers and propagating to the southwest. In addition, the irregularities were found to exhibit finer‐scale structures with secondary bands oriented nearly normally to the primary bands. We investigate the proposition that the primary bands are telltale of Es‐layer structuring caused by neutral Kelvin Helmholtz (KH) instability in the lower thermosphere and that the secondary bands signify secondary KH instability. Results from a 3D numerical simulation of KH support this proposition.